Studies of the dielectrical properties of human tissue types have been made since the late 19th century. All cells and biological tissues conduct electric charge to some degree. The conduction of charge within a cell is known to be affected by a variety of intrinsic and extrinsic factors. The cell has maximal electric conductivity at resistance measurement frequencies equal to 10 kHz and above (B. N. Tarusov. Biological Physics. Higher School Press, 1968). The raising of electric conductivity occurs at the expense of a reduction in capacitance producing complex resistance. At low frequencies of resistance measurement the direct transfer of charge carriers is hindered by the determined structures of a tissue or sub-cell membranes. These structures play a key role in cell polarization phenomena. In contrast, measurements at high frequencies show no influences of polarization phenomena on conductivity.
Thus, it is known that an increase of frequency of a measuring current decreases the complex resistance of a biological tissue or liquid. This phenomenon, named as the dispersion of resistance, is a property of a live cell or tissue. The dispersion of resistance is explained by the presence of polarization phenomena in the biological object--tissue or liquid. At the deterioration of a functional condition of a biological object the ability to achieve polarization decreases. The death of a biological object excludes the dispersion of its resistance and, hence, the ability of the cell to achieve polarization.
Thus, polarization as a phenomenon bears information about the functional condition of a biological object. Therefore, it is possible to evaluate a condition of a biological tissue or liquid with the relation of resistance measured at low frequency to resistance measured at high frequency, that is, with a factor of dispersion.
Devices for definition of a condition of biological tissues and liquids are known which function by measurement of biological tissue and liquid electrical resistance. The methods of electrical impedanceometry, based on measurement of active and reactive elements of the impedance, are widely applied in medicine for diagnosis of pathology of the cardiovascular system, diseases of lungs, etc. However, with the help of present methods of impedanceometry it is possible to receive only general information on changes in organs of the body. Such information in the majority of cases does not reflect the underlying structural changes in tissues. Separate elements of impedance have only been studied, which although reveal the dependence of electrical resistance of tissues on their structure, do not, however, provide sharp diagnostic information. Additionally, in many technical areas, the reliability of data received as a result of measurements of the information is considerably reduced with a reduction in the time of measurement. A reduction in the reliability of resistance measurements is also known to occur with a reduction in the time of measurement.
The majority of known devices for research of a functional condition of biological tissues and liquids, enabling the investigation of electrical parameters of biological tissues and liquids, do not provide sufficient accuracy of measurement of a module of the complete electrical resistance. This is because of errors, caused by drift of the voltage of displacement of zero in the operating amplifier, the influence of "parasitic capacities" in the measuring circuit and non-equivalence of a factor of transformation of signals of detectors under the effect of temporal and climatic factors.
In a known device in European Patent Application 0050353 A1 , the condition of tissue is evaluated on a degree of distinction between the modules of complete electrical resistance of the tissue, measured serially at low and high frequencies. However, with serial measurement of modules of complete electrical resistance at different frequencies, loss or "failure" of information occurs, leading to a doubtful final result, as the condition of a biological object at the small site of measurement does not remain constant in the interval between measurements at high and low frequencies.
A device for researching the gastroenteric tract is known, the purpose of which is increasing the accuracy in diagnosis of peptic ulcer (Certificate of USSR Nr. 1514347). The device consists of a flexible probe with movable half-cylindrical tubes inside the probe case, on the ends of which are fixed metal electrodes, of which the calomel electrode is attached to a hand of the patient and joins to a pH-meter via a switch plug. The design of this device limits the opportunity of the researcher, as it does not permit one to conduct a sampling of histological and cytological material with simultaneous measurement of electrical resistance of the researched object. This device addresses a problem of measurement of the pH of the gastric juice and cannot be used for multifunctional research studies.
Thus, there is a need for an improved multifunctional apparatus and method for obtaining mammalian biological tissue or liquid samples and for diagnosis of the condition of a mammalian biological tissue or liquid employing electrical resistance measurements.